Purification process for improving total yield of curcuminoid colouring agent

ABSTRACT

The present invention pertains to a process of improving the total yield of curcuminoids from curcuminoid-containing material. More specifically, there is provided a process wherein a second residue, previously considered a waste resulting from a crystallization step of a curcuminoid-containing phase, is made useful by improving the coloring properties of this second residue by extraction with hexane and/or methanol at ambient temperature. The process improves the total yield of curcuminoids by 30-40%.

RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119(e) from aprovisional application No. 60/227,293, filed Aug. 24, 2000,incorporated herein by reference to the extent it is consistent withthis application.

FIELD OF INVENTION

The present invention relates generally to the field of naturalcolouring agents and in particular to a purification process forimproving the total yield of curcuminoids in the production ofcurcuminoid colouring agents e.g. from Curcuma rhizomes. Specifically,there is provided a novel process for obtaining improved yield ofcurcuminoids by subjecting curcuminoid-containing materials to at leasttwo separation steps, each of which results in commercially valuablecolouring agents.

TECHNICAL BACKGROUND AND PRIOR ART

Turmeric or “yellow root” is a general term for plants and plantmaterials having a high content of curcuminoids, compounds that have astrong colouring effect and which are used extensively in the colouringof e.g. food products. Turmeric plants belong to rhizomatous Curcumaspecies and have been known for centuries for their flavouring andcolouring properties. The plants are grown commercially, particularly inIndia, but also in Bangladesh, China, Sri Lanka, Indonesia, Taiwan,Haiti, Jamaica and Peru.

It has been found that Curcuma plant materials contain three differentcurcuminoid compounds including, as the predominant colouring compound,curcumin having a strong yellow colour, and minor yellow andbrownish-red components, i.e. the term “curcuminoids” includes curcumin(C), reddish orange and with two methoxy groups; demothoxy curcumin(DMC), orange-yellow with one methoxy group and bis-demothoxy curcumin(BDMC), yellow and without a methoxy group. The relative proportions ofthese three curcuminoid components in the source plant material, inparticular in the rhizomes, have been reported by several groups. Thus,Perotti (1975) found a ratio of 60:30:10, Krishnamurthy et al. (1976)one of 49:29:22 and Govindarajan (1980) found a ratio of 42:24:34.

The Curcuma rhizomes, including the primary or mother rhizomes andseveral long cylindrical multi-branced secondary rhizomes growingdownward from the primary rhizomes, that contain the curcuminoidcompounds in an oily cell phase, are harvested at maturity, typically 8to 9 months after planting.

After harvest, the rhizomes are cured in a process essentiallycomprising cooking the fresh rhizomes in water. This cooking step aidsin producing a product of fairly uniform colour due to the diffusion ofthe yellow pigments from the individual oil containing cells into thesurrounding tissues. After cooking, the material is spread and allowedto dry in the sun. When properly dried, the rhizomes become hard, almosthorny and brittle, and of uniform yellow colour. This cured and driedturmeric product is marketed as bulbs and fingers, each type in polishedand unpolished forms. This turmeric raw material is then made availableto bulk purchase as a starting material for further processing resultingin commercial colouring agents.

Preparing more or less purified solvent extracts of Curcuma plantmaterials, in particular rhizomes as described above, providescommercial curcuminoid-containing colouring agents or compositions.Traditionally, methods for the isolation of curcuminoid colours from theCurcuma starting material involve conventional extraction methodstypically using solvents of defined purity allowed by national andinternational food laws for the processing of food additives, andoptionally further purification step(s).

The curcuminoid-containing phase that is obtained by the aboveextraction methods is in the form of an oleoresin comprising anessential oil containing the curcuminoids. The curcuminoid content ofthe oleoresin is typically in the range of 30-50% by weight. However,the essential oil fraction of the oleoresin has a very strong and bitterflavour, which for many purposes, such as colouring of food products, isundesirable. In order to meet the increasing demand for a highlyconcentrated flavour-free curcuminoid product, the oleoresin may beprocessed further. Thus, the oleoresin may subsequently be subjected toa crystallisation step resulting in the obtainment of a curcuminoidpowder of a relatively high purity (typically >90% by weight) in respectof curcuminoids. The maximum yield of curcuminoids that can be obtainedin this conventional process including the crystallisation step is about60% by weight, i.e. only about 60% of the curcuminoids initially presentin the oleoresin starting material is recovered in thecrystal-containing powder.

The residual material that remains after the above separation ofcurcuminoid crystals consists mainly of the essential oil fraction ofthe oleoresin and a relatively high proportion of the curcuminoidsinitially present in the oleoresin, i.e. 40% by weight or more. However,this residual material, although it has a content of curcuminoids thatconfers to the residual material a yellowish colour, is unsuitable as acolouring agent, not only due to the extensive undesirable flavour, butalso due to its relatively low colouring effect. Furthermore, theresidual material as such is not directly applicable in e.g. foodproducts. Presently, this residual material is, for these reasons, notutilised commercially and it therefore represents a substantial waste ofcurcuminoid colouring material. Evidently, this waste of curcumoids inthe conventional process for providing concentrated and flavour-freecurminoid (or “turmeric”) colouring agents or compositions addssignificantly to the costs of providing such highly desirable products.

A strong industrial need therefore exists to render processes forproviding such useful, and/or pure and concentrated high qualitycurcuminoid products economically feasible. This has been achieved bythe present invention which is based on the discovery that thecurcuminoid-containing waste material can be utilised as a startingmaterial for commercially valuable novel curcuminoid colouring agentshaving excellent and particular colouring properties and, relative tocommercial oleoresin products, a similar or even reduced content ofundesired flavouring compounds.

SUMMARY OF INVENTION

Accordingly, the present invention pertains in a first aspect to aprocess for obtaining an improved total yield of curcuminoid colouringagent, the method comprising the steps of (i) providing acurcuminoid-containing material, (ii) subjecting said material to afirst separation step so as to obtain a curcuminoid-containing phase anda first residue, (iii) subjecting said phase to curcuminoidcrystallisation conditions, (iv) harvesting the thus formed crystals soas to obtain a first curcuminoid colouring agent in the form ofcurcuminoid crystals, and a second residue containing curcuminoids innon-crystalline form, (v) subjecting said second residue to a secondseparation step to obtain a second curcuminoid colouring agent, and athird residue.

In another aspect, the invention provides a colouring agent containingcurcumin, demethoxy curcumin and bis-demethoxy curcumin, the agent isobtainable, as a second curcuminoid colouring agent, by the aboveprocess, the combined amounts of demethoxy curcumin and bis-demethoxycurcumin being above 50% of the total amount of curcuminoids.

DETAILED DISCLOSURE OF INVENTION

A major objective of the present invention is to provide a process forobtaining an improved total yield of curcuminoids for use ascommercially valuable curcuminoid colouring agents. As used herein theexpression “curcuminoid colouring agent” includes a “colouring agent” ora “colouring composition” containing at least one curcuminoid compoundincluding a compound selected from the group consisting of curcumin,demethoxy curcumin and bis-demethoxy curcumin. Furthermore, the“curcuminoid colouring agent” may be obtainable after a first and/or asecond separation step of the provided curcuminoid-containing material.Typically, a commercially valuable colouring agent contains at least 30%by weight of the curcuminoids. Alternatively, the colouring agent maycontain any suitable auxiliary compound e.g. emulsifiers, so as tobecome suitable for specific application e.g. as a food colouringcomposition.

The process of the present invention involves in a first step that acurcuminoid-containing material is provided. As used herein, theexpression “curcuminoid-containing material” includes material derivedfrom any prokaryotic and/or eukaryotic species containing at least onecurcuminoid. Preferably, curcuminoid-containing material derived fromeukaryotic species is derived from plant species. Such plant speciesinclude cultivated or wild plants. In one embodiment of the presentinvention the plant species include plants of the genus Curcuma. Usefulcurcuminoid producing species of this genus include Curcuma longa L., C.aromatica Salisb., C. amada Roxb., C. zedoaria Rosc. and C. xanthorrhizaRoxb.

The plant material is advantageously treated in a way so as to providethe curcuminoids in a uniform and easily accessible condition. Suchtreatments include boiling, curing and subsequent drying of thecurcuminoid-containing plant material prior to separation of thecurcuminoids. The plant starting material can be divided into particlesprior to the first separation step.

It is also possible to provide curcuminoid-containing materials bysubjecting wild type curcuminoid-containing organisms to amutagenisation treatment and select a strain that is capable ofproducing excess amount of one or more of the curcuminoids or a straincapable of producing curcuminoids in a different ratio as compared tothe parent strain. The use of microorganisms or plants that have beengenetically modified to produce curcuminoids as starting material isalso contemplated.

A curcuminoid-containing starting material can be selected that has oneof the curcuminoids e.g. curcumin as the predominant curcuminoid.Additionally, curcuminoid-containing starting material may be providedby mixing curcuminoid-containing material that is derived from differentsources as defined above.

The first separation step in the process of the present inventionincludes any separation procedure resulting in a phase containing thebulk of the curcuminoid compounds of the curcuminoid-containing materiali.e. a curcuminoid-containing phase, and a phase essentially comprisingwaste matter i.e. a first residue, of the curcuminoid-containingmaterial. Where the curcuminoid-containing material is a plant materialthe first residue will be the plant matter devoid of the curcuminoids. Aseparation procedure as used in the present process is typicallyselected from the group consisting of a precipitation, an extraction, afiltration and a distillation. In a preferred embodiment the separationstep is an extraction performed by adding one or more organic solventsto the curcuminoid-containing material. In the present context anextraction may also include a super-critical extraction using carbondioxide as a solvent. After extraction the phases can be separated bye.g. filtering, to obtain the two above phases.

Adding any suitable solvent to the curcuminoid-containing material asdefined above can carry out an extraction. Suitable solvents includearomatic hydrocarbons, aliphatic hydrocarbons such as petroleum ether,heptane, pentane, hexane; chlorinated hydrocarbons such as ethylenedichloride, dichloromethane, trichloro-ethylene; ketones such asacetone; esters such as ethylacetate; alcohols such as methyl alcohol,ethyl alcohol, isopropyl alcohol and n-butanol. It is contemplated thatthe first and second separation step of the present invention alsoencompasses the use of any mixture of solvents.

According to the invention, the resulting curcuminoid-containing phasemay be in any form including a liquid form, a semi-liquid form and asolid form. Preferably, the curcuminoid-containing phase is in asemi-liquid form characterised as an oleoresin comprising an essentialoil fraction containing the curcuminoids. Accordingly, the curcuminoidsare dispersed in an oily phase. This curcuminoid-containing phase is thetraditional colouring and flavouring product used as describedhereinbefore. Although some of the curcuminoids initially present in theplant are retained in the first residue the colour content of theoleoresin is defined as being 100% for the purpose of subsequentcalculations of yield in the further processing of the curcuminoidcontaining phase. The curcuminoids in the oleoresin is, however, dilutedby the presence of the oily phase, and presence of impurities.Accordingly, the purity, or strength, of the oleoresin is about 40% byweight (in the following, all percentages are by weight unless otherwisestated). In the present context the term “pure”, “purity” or “strength”refers to the content by weight of curcuminoids in the sample.

In one embodiment of the present invention curcumin is the predominantcurcuminoid in the curcuminoid-containing phase. The ratio of the threecurcuminoids in the curcuminoid-containing phase is typically: curcuminabout 50-70%, demethoxy curcumin about 10-30% and bis-demethoxy curcuminabout 10-30% the sum of the three compounds being 100%.

In order to obtain a highly concentrated flavour-free curcuminoidproduct, the curcuminoid-containing phase (oleoresin) is processedfurther. The curcuminoid-containing phase obtained by the process of thepresent invention is subjected to curcuminoid separation conditionstypically a crystallisation step, resulting in a curcuminoid powder.Such a separation is a classic separation procedure, which also includea precipitation, a centrifugation, a filtration and a distillation. Theperson of skill in the art can easily select an optimal method for thispurpose.

After subjecting the curcuminoid-containing phase to crystallisationconditions the formed crystals are harvested as a curcuminoid powderwhereby a first curcuminoid colouring agent is formed. This firstcurcuminoid colouring agent is a powder preferably having, in respect ofcurcuminoids, a purity of at least 70% such as at least 80%, 85%, 90% ormore preferably a purity of at least 95% or even 99%. The firstcurcuminoid colouring agent is further characterised in having a typicalratio (as defined above) of the three curcuminoids in the curcuminpowder: curcumin about 65-85%, demethoxy curcumin about 10-30% andbis-demethoxy curcumin about 5-15%, the sum of the three compounds being100%. The yield of this process is about 60% of the cuminoids initiallypresent in the curcuminoid-containing phase (oleoresin).

During the crystallisation process the oily phase, flavouring compoundsand any impurities remain in solution together with the remainingcurcuminoids. This remaining solution is characterised as “a secondresidue” containing curcuminoids in a non-crystalline form. Currently,this second residue is considered a waste due to its very limitedcommercial value.

The improvement provided by the present invention is to obtain acommercially valuable second curcuminoid colouring agent by subjectingthis second residue to a second separation step.

The second residue is in a form selected from a liquid form, asemi-liquid form and a solid form. The content of curcuminoids istypically at least 30% of the curcuminoids initially present in theoleoresin such as at least 35% including at least 40% or at least 50%,or even more if the crystallisation step has not been performed underoptimal conditions.

In accordance with the invention, the second residue is subjected to asecond separation step, which may be carried out using any knownextraction method, and extraction solvent as described hereinbefore. Inone embodiment, extraction of the second residue is performed withhexane as the solvent of choice. Preferably, hexane is applied at atemperature in the range 10-30° C. e.g. about 20° C., optionally understirring of the solution.

The second separation step results in a second curcuminoid colouringagent. This colouring agent can be in a liquid, a semi-liquid or a solidform. Most preferably, the second curcuminoid colouring agent is in asolid form as a “High purity” curcuminoid powder. The “High purity”curcuminoid colouring agent contains the three above curcuminoidcompounds. The ratio of the three compounds in thecurcuminoid-containing phase is typically: curcumin about 35-49%,demethoxy curcumin about 20-30% and bis-demethoxy curcumin about 20-30%,the sum of the three compounds being 100%.

The “High purity” curcuminoid colouring agent has a purity by weight ofcurcuminoids as compared to the second residue including a purity of atleast 25%, such as at least 30% including at least 40% or even at least50%. The total yield of curcuminoids is improved by at least 25% of thecurcuminoids initially present in the curcuminoid-containing phase(oleoresin) such as at least 30%, 35% or even preferably at least 40% ofthe curcuminoids initially present in the curcuminoid-containing phase(oleoresin). It is contemplated that the “High purity” curcuminoidcolouring agent may be diluted to any desired extend using any suitabledilution agent.

The second separation step as described above may alternatively beperformed as a liquid: liquid extraction using e.g. methanol and hexane.Methanol is applied to the second residue to form a mixture which can beextracted by stepwise adding of hexane to the mixture and subsequentseparation of the two phases formed. Preferably an emulsifier is addedto the resulting methanol phase containing the curcuminoids. It ishowever contemplated that any auxiliary agent as described below can beused. After evaporation of the solvent phase a second curcuminoidcolouring agent is formed. This second curcuminoid colouring agent canbe in a liquid and semi-liquid state and is characterized as beingwater/oil soluble/dispersible and hence “Ready to use”.

Auxiliary agents for use subsequent to the liquid:liquid extraction maybe any agent useful in conferring a desired property to the “Ready touse” curcuminoid colouring agent. Desired properties include e.g.solubility properties useful for specific applications. Examples ofuseful auxiliary agents include, but are not limited to oils andemulsifiers. A useful auxiliary agent is a food grade emulsifier such asLecithin, Sorbitan derivatives, Polysorbate or additives like glyceroland Propylene glycol.

The “Ready to use” curcuminoid colouring agent contains the threepreviously described curcuminoid compounds. The ratio of the threecompounds is identical to the ratio as described above for the secondcurcuminoid colouring agent. The purity of the “Ready to use”curcuminoid colouring agent is dependent on the amount of an auxiliaryagent added in the alternative extraction and may be of a purity in therange of 0,25%-40% by weight of curcuminoids as compared to the secondresidue. However, the total yield of curcuminoids by using theliquid:liquid extraction is comparable to the yield obtained for thesecond curcuminoid colouring agent i.e. the total yield of curcuminoidsis improved by at least 25% of the curcuminoids initially present in thecurcuminoid-containing phase (oleoresin) as defined hereinbefore.

In accordance with the invention, the second separation step results ina third liquid residue, essentially void of curcuminoids. This thirdresidue contains the major part of flavouring compounds of the turmericoleoresin. For certain applications this third residue is useful as aflavouring compound. Furthermore, the third residue is valuable as amedicament or for use in the manufacturing of a medicament e.g. fortreating infectious diseases. It is further contemplated that the thirdresidue is useful as a preserving agent e.g. in the preservation of foodproducts or pharmaceuticals.

It is another objective of the present invention to provide a novelcolouring agent containing curcumin, demethoxy curcumin andbis-demethoxy curcumin. The colouring agent is obtainable as a secondcurcuminoid colouring agent, by the process of the invention and thecombined amount of demethoxy curcumin and bis-demethoxy is typicallyabout 50-70% by weight of the total amount of curcuminoids, such as atleast 50%, at least 55%, at least 60%, or at least 70%. This novelcolouring agent may be used directly for colouring purposes as definedbelow. Furthermore, it is to be understood that the features of thecolouring composition as described below applies for the novel colouringagent as well.

A composition comprising such a colouring agent is also encompassed bythe present invention. Such a composition may comprise a furthercolouring agent selected from a natural and/or a synthetic colouringagent. Synthetic colouring agents are normally very pure chemicals withstandardised colouring strength. The colours are available as powders,pastes, granules and solutions and may include compounds e.g. selectedfrom Brillant black, Brown FK, Fast Green, Sunset yellow, Carmoisine andIndigo carmine.

Commercially available natural colouring agents are mixtures of pigmentsfound in nature. Common natural colours include flavonoids, carotenoids,Betalaine pigments, quininoid pigments, porphyrin pigments andmalanoidin pigments.

The synthetic as well as the natural colours may be provided as lakese.g. as aluminium chelates produced by reacting solutions of the colourswith freshly prepared alumina. In general, such lakes have enhancedlight stability over the soluble dye and can be used for colouring drypowder products.

The composition of the invention may e.g. be encapsulated as describedin WO 97/26802 and WO 97/26803 which is hereby incorporated byreference. By this encapsulation, the composition may be applied inenvironments which are normally considered as unfavourable fornon-encapsulated pigments such as e.g. hydrophobic pigments in aqueousenvironments. Furthermore, the encapsulation provides a form wherein thecomposition essentially does not migrate from one to another compartmente.g. in foodstuffs. In one embodiment of the present invention thefurther colouring agent may be a curcuminoid such as e.g. the firstcurcuminoid colouring agent obtained by the process of the presentinvention.

In a further aspect the invention pertains to the use of a compositionaccording to the invention as a colouring agent in the manufacturing ofan edible product. As used herein, the expression “edible product”denotes any solid or liquid food product. Edible products include theproduct types referred to as “nutraceuticals”, “functional foods” or“health improving foods”; i.e. food products or food supplementscomprising components that are considered to confer certain healthimproving characteristics. Such products may be in any conventional formincluding products in tablet or capsule dosage forms that may compriseseparate compartments which can be coloured separately. It will beappreciated that when a composition according to the invention is usedin the manufacturing of such a nutraceutical products, the colouringsubstance can, in addition to its colouring effect, also confer to suchproducts a nutritionally and/or health improving effect. Such healthimproving effects are well described in the art and include antioxidantactivities,

In other useful embodiments, the composition of the invention is used inthe manufacturing of an antiseptic or antimicrobial compound, optionallyby including the third residue in the composition. The term“antimicrobial compound” includes agents that kill micro-organisms(bactericidal) or inhibit the growth (bacteriostatic) of microorganisms.

In a further useful embodiment, the composition according to theinvention is used for the colouring of textiles or polymers. In thepresent context the term “textile” refers to any filament, fibre or yarnthat can be made into fabric or cloth and used in e.g. wearing apparel,household linens and beddings, upholstery, draperies and curtains, wallcoverings, rugs and carpets.

BRIEF DESCRIPTION OF THE DRAWING

The invention is further illustrated in the following non-limitingexamples and in the drawing, where

FIG. 1 shows the process steps of the present invention.

EXAMPLE 1

Analysis of Curcuminoid Contents in Samples of FreshCurcuminoid-Containing Plant Material, Turmeric Oleoresins, CurcuminPowders and Waste (the Second Residue).

Information from industrial processes to obtain curcuminoid colouringagents and information of the curcuminoid contents in the end product isvery limited as the processes are regarded as restricted information bythe firms. Accordingly, a study of the products on the market wasperformed, covering different raw materials, turmeric oleoresins andcommercial curcumin powders in order to gain information on thecurrently used processes for extraction of the colouring compounds fromthe raw material. Furthermore, samples of the second residue resultingfrom the crystallisation process was obtained and analysed.

The colouring compounds of turmeric, as described hereinbefore, consistsof the three colouring compounds curcumin (C), demethoxycurcumin (DMC)and bis-demethoxycurcumin (BDMC). These colours were synthesised, andusing HPLC with these synthetic compounds as standards, the curcuminoidcompositions of the different samples were estimated.

Results of analysis of curcuminoid ratios in different raw materials arepresented in table 1. The content of C was found to be in the range of52-63%, the content of DMC was in the range of 19-26%, and the contentof BDMC was in the range of 19-28%. The overall picture of thedistribution of the three curcuminoid compounds is relative similar inthe analysed samples. Small variations in the curcuminoid contentbetween the individual samples were observed and this was most probablydue to the nature of the raw material, time of harvest etc.

TABLE 1 Curcuminoid composition of raw materials from India. The resultsare based on synthetic standards and the values are expressed as weight% of the total colour content. C DMC BDMC Trade name (%) (%) (%) DesiKadappa finger turmeric (polished) 58.7 22.6 18.7 Salem finger turmeric(polished) 61.0 19.7 19.4 Rajpuri finger turmeric 52.8 21.5 25.7Nezamabad finger turmeric 62.2 20.7 17.1 Sadashipet finger 52.9 23.723.4 AFT (bulp split) 62.4 19.2 18.4 Barsi Kocha turmeric 52.4 19.7 27.9Panamgaly turmeric (Erode) 63.2 18.8 18.0 Erode Ghatta turmeric 61.118.7 20.1 Erode finger turmeric 59.0 21.8 19.3 Madras finger turmeric(MFT) 60.1 19.7 20.2 Meghalaya split turmeric 54.5 26.3 19.2 SalemPanamgali 59.8 20.6 19.6 Alappy finger turmric (AFT) 60.7 20.2 19.1

The colour content and composition in different commercial andexperimental samples of turmeric oleoresins, powders and wastes arepresented in table 2. This table illustrates that the curcuminoidcomposition in the first 4 oleoresins is within the limits observed forthe raw material, dried rhizomes. The last 2 oleoresins are experimentalproducts with pure curcumin powder added.

TABLE 2 Curcuminoid content in different commercial and experimentalsamples of turmeric oleoresins, curcuminoid powders and waste materials,the value of C, DMC and BDMC are expressed as % weight of the totalcolour content. Curcuminoids C DMC BDMC Samples type (% weight) (%) (%)(%) A oleoresin 41.61 61.9 21.0 17.1 B ″ 39.32 64.3 20.1 15.6 C ″ 37.4454.0 23.5 22.4 D ″ 40.26 61.5 19.1 19.4   E* ″ 37.31 72.7 17.2 10.1   F*″ 45.46 73.3 16.6 10.1 H powder 95.94 81.6 15.9 2.5 I ″ 96.67 87.4 11.21.4 J ″ 95.13 77.1 17.7 5.2 K ″ 97.03 71.1 19.3 9.6 L ″ 93.81 73.8 19.17.1 M ″ 96.21 81.3 16.2 2.5 N ″ 91.60 76.3 19.7 4.1 O ″ 94.40 77.1 18.34.6 P ″ 93.66 80.7 16.5 2.8 Q ″ 96.60 85.7 12.6 1.7 R ″ 89.90 80.4 15.74.0 S ″ 90.99 80.4 15.8 3.8 U waste 14.58 48.0 24.6 27.4 V ″ 13.40 41.025.4 33.6 X ″ 17.87 28.9 26.6 44.5 *: Added curcuminoid powder to obtaina desirable colouring strength of the oleoresin.

As illustrated by the table (table 2) the ratio of curcuminoids in theoleoresin was equal to the ratio found in the raw material (table 1).However, the curcuminoid powders showed a completely different ratio ofcurcuminoids as compared to the oleoresins and the raw material. Thecontent of C was between 71-88%, the content of DMC between 11-20% andthe content of BDMC between 1-10%. The variation in curcuminoid contentbetween the different samples is probably dependent on the turmericoleoresin and the pro??cess of crystallisation (solvent,solvent/oleoresin ratio, parameter settings during processing etc.).

In the powder product the content of C was increased, the content of DMCreduced and the content of BDMC also reduced as compared to the contentof the curcuminoids in the fresh starting material and the oleoresins.

This observation explains the low yield in the process where theturmeric oleoresin is converted into a turmeric powder. Acrystallisation process of a chemical substance containing a maincomponent at approximate 60% by weight and 2 other components inapproximate equal amounts can not be expected to result in a yield ofmore than 60%. The most abundant component in a mixture of chemicalcompounds tends to crystallise in a more pure form than other componentspresent. Further use of solvents and/or recrystallisation will alwayslead to a relatively poor yield and this yield will depend on theconcentration of the main component and the number ofrecrystallisations.

As a result of the conventional crystallisation process a second residueis obtained. This “waste” was analysed and table 2 shows the curcuminoidcontent hereof. As illustrated, a completely different picture isobtained. Here the ratio of the 3 different components was inapproximate the same amounts. The ratio of the three curcuminoids (C,DMC and BDMC) was found to be 40:25:35, respectively. Hence, a furthercrystallisation of this composition can not lead to an increase ofcurcumin-crystals.

Table 2 further illustrates the purity, or strength, of the colouringcompositions, calculated as the total percentage of curcuminoids in thematerial (% weight). It appears from the table that the purity of theoleoresin is about 40% by weight, of the powder about 95% by weight andof the waste about 15% by weight. As described above, and as illustratedby the table, the strength of the waste is unacceptable as acommercially valuable product. Although, 40% of the original 100% ofcurcuminoids in the oleoresin is contained in the waste, thecrystallisation process leaves the remaining curcuminoids in a solutionwith all impurities, the essential oil fraction and all flavouringcompounds. Accordingly, the colouring strength of the solution is only15% by weight and furthermore, the solution is strongly flavoured and assuch of an unacceptable quality.

As mentioned above, there is a great industrial interest in providingthe curcuminoids in the second residue in a commercially valuable form.Different approaches to extracting the oil fraction from the curcuminoidfraction were tested and the second residues resulting from thecrystallisation processes were used as a starting material in thefollowing 3 Examples.

During the attempts to extract curcuminoids from the waste, the contentsof the curcuminoids were analysed spectrophotometrically.

EXAMPLE 2

Improving Yield by Refluxing the Second Residue in Hexane.

To the second residue hexane was added in equal amounts in a flask. Themixture was refluxed for 30 minutes. During reflux an oily phase at thebottom was observed. The sample was cooled and left for 1 month. Asticky precipitate containing the major part of curcuminoids wasobserved. The experiment clearly showed that refluxing in concentratedhexane was not adequate to obtain a useful product.

EXAMPLE 3

Extraction of the Hexane Extractable Oil by Changing the Hexane/AcetoneRatio.

Hexane and acetone was added to the second residue (12:3:10). Themixture was refluxed for a couple of hours and left overnight. Thesolvent contained only small amounts of curcuminoids and the fraction ofacetone was increased in two steps to an amount that resulted in amixture of hexane, acetone and the second residue in a ratio of(12:8:10), respectively. After adding half of the acetone the mixturewere refluxed for 1.5 hours, then the remaining acetone was added andthe mixture was refluxed for 1.5 hours. The sample was transferred to arefrigerator and left overnight. After 3 month in refrigerator theresult was a sticky useless powder.

EXAMPLE 4

Extraction with Hexane at Ambient Temperature.

While stirring, the second residue was added to hexane in a ratio of 1:4in a flash. The mixture was stirred at ambient temperature for 2 days. Apowder filtrate developed, the filtrate was isolated and washed withhexane.

The hexane was evaporated and the powder filtrate was split into two.One was dried at 40° C. and the second was dried at 70° C. Drying at 40°C. resulted in a yellow powder which contained 30.5% curcumin. Thispowder tended to get darker with time and caramelise.

Drying at 70° C. resulted in a dark brown powder which contained 31.0%curcumin.

Total yield of this process was found to be 96% (relative to the initialcontent of curcuminoids present in the second residue). The ratio of thethree curcuminoids was found to equal the ratio found in the secondresidue “waste” (illustrated in Table 2).

The obtained second curcuminoid colouring agent was characterised as a“High purity” colouring agent.

EXAMPLE 5

Extraction with Methanol at Ambient Temperature.

An alternative method of extraction is a liquid:liquid extractionperformed using methanol and hexane. 180 Kg of the second residue waspumped to a production tank. 200 Kg methanol was added. The mixture wasstirred at ambient temperature for 15 minutes. 800 L of hexane was addedand after stirring for 1 hour the phases were separated using a bottomvalve. The methanol phase was washed with hexane and subsequentseparated in two further steps. In the first step 800 L of hexane wereadded in the second step 1000 L of hexane was added. The mixture werestirred for 30 minutes and separation was performed after 1 hour.

The resulting methanol phase was pumped together with 300 Kg polysorbateto an evaporator. The solvent was removed by heating to 85° C. undervacuum. A total of 370 kg “Ready to use” watersoluble curcumin productwas obtained by the above method.

A subsequent extraction identical to the above liquid:liquid extractionwas performed. The starting material included the methanol/oleoresinphase separated from the hexane extract from the previous extraction,another 180 kg of the second residue and 300 Kg of metanol. Thissubsequent procedure improved the total yield of the extraction as aminor part of curcuminoids are present in the hexane phase of the firstextraction. However, A total yield of 77% was obtained by the firstextraction the total yield by running the extraction in two series was95% of the curcuminoids present in the second residue.

The above extraction resulted in a water soluble second curcuminoidcolouring agent with a colour content of 10%. These characteristicsrender the agent useful for direct application in e.g. food products,accordingly the second curcuminoid colouring agent as obtained by theliquid:liquid extraction is characterised as a “Ready to use” colouringagent.

In Conclusion

The examples show that it is possible to obtain an improved yield of theprocess of the invention. The total yield of the entire process startingwith a curcuminoid-containing phase (the oleoresin) may be close to 100%using the process of the invention where the remaining curcuminoids inthe waste is harvested as a second curcuminoid colouring agent in a“Ready to use” or “High purity” form as shown in table 3 whichsummarises the results.

TABLE 3 A summary of the purity of the different products involved inthe process. curcuminoid frac- material oil fraction (%) tion (%) Sum(%) oleoresin 52.9 39.8 92.7 powder  0 97.7 97.7 “waste”, second residue64.0 14.6 78.6 regenerated waste, 47.0 30.5 77.5 Example 4 regeneratedwaste, 47.4 31.0 78.4 Example 4 regenerated waste, 49.7* 38.0 87.7Example 5 *Corrigated for the content of polysorbate in the final “Readyto use” colouring agent.

As illustrated in table 3 the colouring strength of the oleoresin isabout 40% by weight as described before. The “waste” was previouslyconsidered a useless product due to the poor colouring properties. Theprocess of the present invention leads to a regenerated waste which hasa purity and thereby a colouring strength which is comparable to thestrength of commercial oleoresin product. This implies that theregenerated waste may be sold as an oleoresin or, alternatively used asa novel product with particular and new colouring properties due to thealtered ratio of the three curcuminoids.

The Table further illustrates that some presently unknown impurities arein the samples as the sum of the oil fraction and the colour fraction is70-90.

REFERENCES

Govindarajan (V. S. Turmeric-Chemistry, Technology and Quality, CRCCrit. Rev. Food Sci. Nutr., 12, 199 (1980), p. 257).

Krishnamurthy N., Mathew A. G., Nambudiri E. S., Shivasankar S., LewisY. S. and Natarajan C. P. 1976. Oil and oleoresin of turmeric. Trop.Sci. 18:37.

Perotti A. G. 1975. Curcumin—a little known but useful vegetable colour.Ind. Aliment. Prod. Veg. 14:66.

What is claimed is:
 1. A process for obtaining curcuminoid colouringagents, comprising the steps of: (i) providing a curcuminoid-containingmaterial, (ii) subjecting said material to a first separation step so asto obtain a curcuminoid-containing phase and a first residue, (iii)subjecting said phase to curcuminoid crystallization conditions to formcrystal thereof, (iv) harvesting the thus formed crystals so as toobtain a first curcuminoid colouring agent in the form of curcuminoidcrystals, and a second residue containing curcuminoid in non-crystallineform, (v) subjecting said second residue to a second separation step toobtain a second curcuminoid colouring agent, and a third residue.
 2. Aprocess according to claim 1 wherein the curcuminoid-containing materialis a curcuminoid-containing plant material.
 3. A process according toclaim 2 wherein the curcuminoid-containing plant material is derivedfrom a plant species of the genus Curcuma.
 4. A process according toclaim 2 wherein the curcuminoid-containing plant material is derivedfrom Curcuma roots.
 5. A process according to claim 2 wherein thecurcuminoid-containing plant material is a cured and dried plantmaterial.
 6. A process according to claim 1 wherein thecurcuminoid-containing material is subjected to a first separation stepwhich comprises one of a precipitation, an extraction, a filtration, ora distillation.
 7. A process according to claim 6 wherein the extractionis performed using an organic solvent.
 8. A process according to claim 7wherein the organic solvent comprises one of an aromatic hydrocarbon, analiphatic hydrocarbon, a chlorinated hydrocarbon, an alcohol, a ketone,an ester, or any mixtures thereof.
 9. A process according to claim 1wherein the curcuminoid-containing phase is in a form comprising one ofa liquid phase, a semi-liquid phase or a solid phase.
 10. A processaccording to claim 1 wherein the curcuminoid-containing phase is anoleoresin.
 11. A process according to claim 1 wherein thecurcuminoid-containing phase comprises at least 30% of curcuminoids byweight.
 12. A process according to claim 11 wherein thecurcuminoid-containing phase comprises curcumin, demethoxy curcumin andbis-demethoxy curcumin.
 13. A process according to claim 12 whereincurcumin is the predominant curcuminoid.
 14. A process according toclaim 13 wherein curcumin constitutes at least 50% of the curcuminoidsin the curcuminoid-containing phase.
 15. A process according to claim 11wherein the curcuminoid-containing phase comprises curcumin, demethoxycurcumin and bis-demethoxy curcumin in a ratio of about 60:20:20.
 16. Aprocess according to claim 1 wherein the first curcuminoid colouringagent has a purity of at least 80% in respect of curcuminoids.
 17. Aprocess according to claim 1 wherein the first curcuminoid colouringagent comprises curcumin, demethoxy curcumin and bis-demethoxy curcuminin a ratio of about 75:20:5.
 18. A process according to claim 1 whereinthe second residue is in liquid or semi-liquid form.
 19. A processaccording to claim 18 wherein the second residue comprises at least 10%curcuminoids by weight.
 20. A process according to claim 1 wherein thesecond residue is subjected to said second separation step comprisingone of a precipitation, an extraction, a filtration, a crystallisation,a recrystallisation and a distillation.
 21. A process according to claim20 wherein the extraction is performed using an organic solvent.
 22. Aprocess according to claim 21 wherein the extraction is performed with asolvent comprising one of an aromatic hydrocarbon, an aliphatichydrocarbon, a chlorinated hydrocarbon, an alcohol, a ketone, an ester,or any mixtures thereof.
 23. A process according to claim 21 wherein theorganic solvent is hexane.
 24. A process according to claim 23 whereinhexane is applied at a temperature of about 20° C.
 25. A processaccording to claim 20 wherein the extraction is performed as aliquid:liquid extraction.
 26. A process according to claim 25 whereinthe extraction is performed using methanol and hexane at ambienttemperature.
 27. A process according to claim 26 wherein an auxiliaryagent is added to the methanol including the colouring agents after theextraction.
 28. A process according to claim 27 wherein the auxiliaryagent is a food grade additive.
 29. A process according to claim 1wherein the second curcuminoid colouring agent is in a form comprisingone of a liquid phase, a semi-liquid phase or a solid phase.
 30. Aprocess according to claim 1 wherein the second curcuminoid colouringagent is soluble and dispersible in water and oil.
 31. A processaccording to claim 1 wherein the second curcuminoid colouring agentharvested from the second residue is a curcuminoid powder that has apurity by weight of curcuminoids of at least 25%.
 32. A processaccording to claim 1 wherein the second curcuminoid colouring agentcomprises curcumin, demethoxy curcumin and bis-demethoxy curcumin.
 33. Aprocess according to claim 32 wherein the predominant curcuminoids ofthe second curcuminoid colouring agent are demethoxy curcumin and/orbis-demethoxy curcumin.
 34. A process according to claim 33 wherein thesecond curcuminoid-colouring agent comprises curcumin, demethoxycurcumin and bis-demethoxy curcumin in a ratio of 40:25:35.
 35. Aprocess according to claim 1 wherein the third residue is a liquidessentially void of curcuminoids.
 36. A process according to claim 1wherein the third residue comprises flavouring compounds.
 37. A processaccording to claim 1 wherein the total yield of the curcuminoidcolouring agents is improved by at least 10% relative to a conventionalprocess for preparing curcuminoid-coloring agents.
 38. A processaccording to claim 7 wherein the organic solvent is selected from thegroup consisting of an aromatic hydrocarbon, an aliphatic hydrocarbon, achlorinated hydrocarbon, an alcohol, a ketone, an ester, and anymixtures thereof.
 39. A process according to claim 1 wherein thecurcuminoid-containing phase is in a form selected from the groupconsisting of a liquid phase, a semi-liquid phase and a solid phase. 40.A process according to claim 1 wherein the second residue is subjectedto a second separation step comprising a precipitation, an extraction, afiltration, a crystallisation, a recrystallisation or a distillation.41. A process according to claim 3, wherein the genus Curcuma includesthe species Curcuma longa L., C. aromatica Salisb., C. amada Roxb., C.zedoaria Rosc. or C. xanthorrhiza Roxb.
 42. A process according to claim4 wherein the curcuminoid-containing material is derived from theprimary rhizome, the secondary rhizomes and any mixtures thereof.